1. Field of the Invention
The field of art to which this invention pertains includes a shift control system in combination with a transmission having a multiple input portion and a multiple output portion, each of which in turn contains a plurality of constant-mesh change speed gears to provide for a plurality of drive ratios in response to movement of the operator's shift lever or the like.
2. Description of the Prior Art U.S. Pat. No. 4,000,662, issued on Jan. 4, 1977, which is also assigned to the assignee of the present invention, discloses a highly advantageous form of transmission having a basic structure which provides axially aligned input and output shafts together with a single aligned countershaft as well as first, second and third input gears and a plurality of forward output gears with one of the forward output gears also being capable of serving as one of the input gears. First, second and third driven countershaft gears are in constant mesh with respective ones of the input gears and each one of a plurality of driving countershaft gears is in constant mesh with a separate one of the forward output gears, with one of the driving countershaft gears also being capable of serving as one of the driven countershaft gears. Multiple clutch means are utilized for selectively drivably connecting the countershaft with one of the input gears and for selectively drivably connecting the output shaft with the countershaft.
The multiple use of most of the gears of this transmission together with the triple input feature and the single countershaft permits utilization of a transmission housing that has but two through bores, and in one embodiment, all of the components for a nine speed forward and three speed reverse transmission can be located completely within a standard five speed forward-one speed reverse transmission housing.
The multiple use of the gears of this transmission, requires a sophisticated shift control system, especially if this system is of the preselector or semi-automatic type wherein shifts between drive ratios are made in response to the movement of an operator's shift lever and the release of the torque on the drive train.
Related prior art transmissions and control systems therefore are described in U.S. Pat. Nos. 2,974,766; 2,297,026; 2,943,719; 2,943,500; 2,226,660; 3,039,320; 3,422,939; 3,795,153; and 3,941,007.